The use of computers, PDAs (Personal Digital Assistant), GPSs (Global Positioning System), mobile terminals and other kinds of data processing systems has increased strongly in recent years. At the same time the size of these systems and devices has become smaller, whereupon there has arisen some problems with the size of the screens and displays of these apparatus. Visual acuity of human being is quite limited so that individual can't see small objects clearly and thus the size of the displays must be kept moderately big. There are, however, some other problems with small displays and also with big displays, when a large number of application windows are operated parallel, because there is not enough space in the display for showing all operated applications, windows or other user interface elements simultaneously.
There are several prior art solutions for solving the problems mentioned above, like a taskbar for example in Microsoft Windows™ operating systems and different kinds of task lists. There are also so called virtual desktops, which can be larger than the physical screen, whereupon user can switch between the different user interface elements, applications or windows by scrolling the virtual desktop in horizontal and vertical directions.
A solution is also known where windows can be dragged outside of the screen so that a part of them remains on the display. In addition, there is a solution where the windows and other user interface elements can be stacked on top of each other, the desired window or other element can be selected by switching between the windows by using, for example, some button combination.
However, there are certain disadvantages and problems related to the prior art solutions that were described above. For example, in solutions where users are allowed to have a large number of windows, applications and other user interface elements on top of each other, the switching between e.g. the windows can be carried out by using buttons and button combinations (such as alt+tab in Microsoft Windows™ operating systems) that requires much knowledge about how the operating systems work. With many windows stacked, it is also difficult to know how many active windows and applications there actually are, what they contain, what their purpose is and what is the state of the applications.
Furthermore, in applications, which contain larger virtual desktop than the physical screen or display the scrolling the desktop is typically slow and tedious and if the virtual desktop is much larger than the physical screen (which can be true with small screens), it becomes very difficult to remember the location of a window and to find it. In systems, which allow the shifting the windows so that part of the window is still on the screen, the screen space or display easily becomes confused.
There are also some arrangements with a task list that shows all the active windows, applications and other user interface elements. This kind of arrangements require a way to activate the task list, and again the list of active tasks can be so long that it requires scrolling.